Changeset 700eaa9 in mainline

Timestamp:

2008-10-26T17:26:17Z (16 years ago)

Author:

Martin Decky <martin@…>

Branches:

lfn, master, serial, ticket/834-toolchain-update, topic/msim-upgrade, topic/simplify-dev-export

Children:

23b56ca

Parents:

f772105e

Message:

proper FAT16 boot sector initialization

File:

• tools/mkfat.py (modified) (3 diffs)

tools/mkfat.py

@@ -35 +35 @@
 import random
 import xstruct
+
+def align_up(size, alignment):
+        "Return size aligned up to alignment"
+        
+        if (size % alignment == 0):
+                return size
+        
+        return (((size / alignment) + 1) * alignment)
+
+def subtree_size(root, cluster_size):
+        "Recursive directory walk and calculate size"
+        
+        size = 0
+        files = 0
+        
+        for name in os.listdir(root):
+                canon = os.path.join(root, name)
+                
+                if (os.path.isfile(canon)):
+                        size += align_up(os.path.getsize(canon), cluster_size)
+                        files += 1
+                
+                if (os.path.isdir(canon)):
+                        size += subtree_size(canon, cluster_size)
+                        files += 1
+        
+        return size + align_up(files * 32, cluster_size)
+
+def root_entries(root):
+        "Return number of root directory entries"
+        
+        return len(os.listdir(root))
 
 BOOT_SECTOR = """little:
@@ -77 +109 @@
                 return
         
+        sector_size = 512
+        cluster_size = 4096
+        
+        root_size = align_up(root_entries(sys.argv[1]) * 32, sector_size)
+        size = subtree_size(sys.argv[1], cluster_size)
+        fat_size = align_up(size / cluster_size * 2, sector_size)
+        
+        sectors = (cluster_size + 2 * fat_size + root_size + size) / sector_size
+        
         outf = file(sys.argv[2], "w")
         
@@ -82 +123 @@
         boot_sector.jmp = [0xEB, 0x3C, 0x90]
         boot_sector.oem = "MSDOS5.0"
-        boot_sector.sector = 512
-        boot_sector.cluster = 8 # 4096 bytes per cluster
-        boot_sector.reserved = 1
+        boot_sector.sector = sector_size
+        boot_sector.cluster = cluster_size / sector_size
+        boot_sector.reserved = cluster_size / sector_size
         boot_sector.fats = 2
-        boot_sector.rootdir = 224 # FIXME: root directory should be sector aligned
-        boot_sector.sectors = 0 # FIXME
+        boot_sector.rootdir = root_size / 32
+        boot_sector.sectors = (sectors if (sectors <= 65535) else 0)
         boot_sector.descriptor = 0xF8
-        boot_sector.fat_sectors = 0 # FIXME
-        boot_sector.track_sectors = 0 # FIXME
-        boot_sector.heads = 0 # FIXME
+        boot_sector.fat_sectors = fat_size / sector_size
+        boot_sector.track_sectors = 63
+        boot_sector.heads = 6
         boot_sector.hidden = 0
-        boot_sector.sectors_big = 0 # FIXME
+        boot_sector.sectors_big = (sectors if (sectors > 65535) else 0)
         
-        boot_sector.drive = 0
+        boot_sector.drive = 0x80
         boot_sector.extboot_signature = 0x29
         boot_sector.serial = random.randint(0, 0xFFFFFFFF)